NCAA Basketball. Its a tournament of 64 teams with a few rounds. All the teams are in set up in 4 "regions", and all of this together makes up the bracket. 1 winner for the whole thing, of course. Oh, and lets go Georgetown!
yeah, most people start a pool where you fill out a bracket and have a buy in, the person who predicts the most games right wins the money, im winning in mine right now woohoo